The instant invention generally relates to governing the amount of a plurality of colorants such as dyes applied to a material to control the reflectance of the material over the entire range of the visible spectrum, and more particularly to controlling the color of a paper web.
In prior art color control systems, the coloration model is generally a 3.times.3 matrix expressing the relationship between the flows of three judiciously selected colorants and the three color coordinates of one of the common color spaces. These coordinates may be, for example, Hunter Laboratories L, a, b or C.I.E. L*, a*, b* or chromaticity x, y, z or tristimulus X, Y, Z.
Metameric effects are the greatest problem since two differently appearing colors may have the same color coordinates in a given color space. This occurs not only under different illumination and observer conditions, but also simply due to the method in which the various color coordinates are derived.